The more gain you design into the system, the sharper the bandpass Q gets and the narrower the bandwidth.

I would think bandwidth concerns would limit things before you reach a limit in gain. For really high gains, box damping may become a significant factor, you would need a really airtight, stiff box and a very good flowing port to achieve the predicted results.

Tell us what the motivation for the question is, you might get an answer to a question you didn't ask, but wanted to.

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